US president says it's the 'last chance' for US and Europe to come up with agreement to strengthen 2015 nuclear deal.

US President Donald Trump has decided he will continue sanctions relief for Iran, keeping the 2015 landmark nuclear deal in place for the time being.

The White House said on Friday that Trump will waive the sanctions against Iran for the "last time", unless an agreement can be reached between the US and Europe within the next 120 days that would strengthen the nuclear deal.

"Despite my strong inclination, I have not yet withdrawn the United States from the Iran nuclear deal," Trump, who has repeatedly threatened to "rip up" the deal, said in a statement on Friday.

"Instead I have outlined two possible paths forward: either fix the deal's disastrous flaws, or the United States will withdraw," he added.

"This is the last chance. In absence of such an agreement [between the US and European powers], the United States will not again waive sanctions in order to stay in the Iran nuclear deal."

The announcement came as the US Treasury imposed sanctions on 14 Iranian individuals and companies, including the head of Iran's judiciary.

2015 nuclear deal

The 2015 Iran nuclear deal was struck between the US under the administration of former President Barack Obama, Iran and five other countries. It prevents Iran from developing nuclear weapons while offering sanctions relief to allow the Islamic Republic to participate in international commerce and banking.

Under US law, the president is required to renew the waiver on sanctions every 120 days. The last time Trump issued a waiver was in September 2017.

In October of last year, Trump refused to recertify that Iran was in compliance with the agreement, saying the agreement was "one of the worst and most one-sided transactions the US has ever entered into".

But Federica Mogherini, the European Union's foreign policy chief, said the "deal is working; it is delivering on its main goal, which means keeping the Iranian nuclear programme in check and under close surveillance".